With the optimization and upgrading of the GSM network, there are some areas in which the GSM network supports the R9 protocol, one of the new features added in the R9 protocol is to support the PS handover, and it needs to provide users with non-perceivable channel handover capability.
Prior to the version of R9, there is no protocol supporting the PS handover, and if the original channel quality deteriorates, it is necessary to switch the channel with the cell reselection method, that is, after the terminal detects that the original channel's quality deteriorates, the terminal itself initiates a reselection process; in the IDLE state, it synchronizes with the handover target cell, interacts with the handover target cell to acquire a system message of said handover target cell; and resides in the handover target cell according to the acquired system message of the handover target cell. Since it is time-consuming for the terminal interacting with the handover target cell to acquire the system message of said handover target cell, it will cause the entire reselection process interrupts the PS service for some time, for example, a user is downloading, and such download service will be interrupted for some time, which is not conducive to the user experience.
To make the terminal support the PS handover, the existing technical solutions usually modify the overall implementation of the terminal baseband chip and add all the codes that support this feature, which has a relatively large impact scope, which is not good for the system stability and increases the R&D and testing costs.